How to compare two versions of a PDF
Choose the original PDF first, then choose the revised version. This order matters because the results describe changes from the original to the revision. Drop each file onto its own area or click the area to browse. The tool accepts files up to 40 MB and 100 pages each. It reads and renders the PDFs in your browser, so the files stay on your device.
Click Compare PDFs. The results start with a count of page pairs with detected differences. Use the Page pair menu to move between pages. It lists unchanged pages alongside changed, added, and removed pages. Each selected pair shows the original page, the revised page, and a visual comparison. Red marks rendered pixels that differ by more than the tool's color threshold. Look at the two original previews for context around each red mark.
How visual changes and text changes work
The visual comparison can show differences in images, placement, and text appearance. It renders both pages at a fixed preview resolution and compares their pixels. Page size is checked separately. A small shift can affect several pixels, while a tiny change can be hard to see at preview resolution. The percentage refers to the compared image area and gives an idea of the size of the visual change.
The text comparison extracts selectable text, groups it into lines, and looks for additions and removals. If a line changes, the old line appears as removed and the revised line appears as added. Spaces are normalized for text comparison. On a scanned page without a text layer, use the visual comparison. The tool can render a scan, but it cannot transcribe the text inside the image. PDF comments and other annotations are excluded from the visual comparison.
Worked example for a revised quote
Suppose a supplier sends a new version of a three-page quote. Choose yesterday's quote as the original and today's quote as the revision. If the supplier changed a price on page two and left the other pages alone, the summary may show one changed page pair. Select page two to see the previous price line and the replacement line. Use the red preview to check whether the supplier also moved or reformatted the price block.
If the supplier also added a fourth page, it appears as an added page. The downloadable text summary records the page counts and detected differences for each pair. Use the page previews to see the context before sharing the summary with someone else. For a digital quote with tabular pricing, the PDF to Excel converter can help pull the rows into a workbook for a separate review.
Common mistakes when reviewing revisions
The tool pairs page one with page one, page two with page two, and so on. If someone inserts a page in the middle, later pages can appear changed because their numbers have shifted. Check the revised page order before interpreting a long run of changes. A page added at the end is easier to interpret because the earlier pages stay aligned.
A detected pixel change can come from a new font, different margins, or a PDF export setting. Conversely, page previews and extracted text cover only part of a PDF. Review any comments, attachments, forms, or signatures separately in a PDF reader when those features matter. For tiny edits or fine print, open the original PDF at a larger zoom.
Frequently asked questions
Are my PDFs uploaded anywhere?
No. The browser downloads the PDF processing library and compares the files locally. Your PDF contents stay on your device.
Can I compare scanned PDFs?
Yes. The visual comparison can show changes between scans. The text panel needs a selectable text layer, and this tool does not perform OCR.
Does it automatically match moved pages?
Pages are paired by number. An insertion or deletion can shift the comparison for pages that follow it.
Why did a line appear twice in the results?
A changed line is shown as the removed original and the added replacement so you can read the two versions.
What is in the downloadable summary?
It includes the original and revised file names, the page counts, and a brief description of detected changes for each page pair.